A persistent vegetative state (commonly, but incorrectly, referred to as "brain-death") sometimes follows a coma. Individuals in such a state have lost their thinking abilities and awareness of their surroundings, but retain non-cognitive function and normal sleep patterns. Even though those in a persistent vegetative state lose their higher brain functions, other key functions such as breathing and circulation remain relatively intact. Spontaneous movements may occur, and the eyes may open in response to external stimuli. They may even occasionally grimace, cry, or laugh. Although individuals in a persistent vegetative state may appear somewhat normal, they do not speak and they are unable to respond to commands.
http://www.ninds.nih.gov/disorders/coma/coma.htmSounds exactly like Schaivo. I read that 7 of her 8 doctors over the years had diagnosed her as having such. The one doctor saying otherwise was brought in by her parents. Anyway, its good to have a better understanding of what is going on when debating the cult loonies.